Echo web site shows a cs 510 and a cs 530 but no cs 520.
You can down load the owners manuals there.

Thanks for the reply. I have the manuals. Ordered a repair manual, clutch removal tool and a new oil pump. It fixed it right up. I have learned a lot about chain saw repair since the post. LOL

Rebuilt a carb, sharpened about 20 chains. Pulled limiters, performed proper carb adjustment for muffler mods. I now have 6 screaming saws now that love to eat up Oak. Chopped about 6 cords of wood. The 520 is one of my favorite saws.

Thanks again,

Jim